T29. Radial mixed nerve conduction study: Preliminary findings in controls and patients

Abstract

Introduction Radial nerve, with fibers from nerve roots C5-T1, is a continuation of the posterior cord of the brachial plexus. It divides into deep (motor) and superficial (sensory) branch after it passes through the cubital fossa. A short segment along the spiral groove before branching comprises mixed sensory (afferent) and motor (efferent) fibers. In this study, we perform radial mixed nerve conduction study (RMNCS) in normal subjects, in comparison with patients with radial neuropathy and brachial plexopathy. Methods RMNCS was performed with surface electrodes. The stimulation cathode was placed 1 cm above the cubital fossa, and the recording cathode at 7 cm above, along the spiral groove. Distal latency (DL), amplitude (Amp) and conduction velocity (CV) were compared between controls and patients. Results Mean (standard deviation) of 17 healthy controls (mean age: 48; range: 20–77) were 1.12 (0.21) ms for DL, 4.24 (0.21) mV for Amp and 63.35 (5.04) m/s for CV. Of 7 patients with suspected radial neuropathy, all 3 with the confirmed diagnosis showed abnormally reduced amplitude or absent radial mixed nerve responses. Of 5 patients with suspected brachial plexopathy, all 3 with the confirmed diagnosis showed absent radial mixed nerve responses. Conclusion This is the first study to demonstrate the feasibility of RMNCS and its value in the evaluation of radial neuropathy and brachial plexopathy as diagnostic adjuncts. Further studies are justified to define the role of RMNCS in other neuropathic conditions.